The present invention relates to a device for treating a blood vessel, the device being of the type comprising:                at least one tubular endoprosthesis that is deployable between a retracted state and an expanded state;        a hollow prop which extends longitudinally between a proximal end and a distal end, which prop is provided in the vicinity of its distal end with at least one transverse retaining opening;        at least one releasable filamentary line forming at least one tightening loop which surrounds at least part of the endoproathesis, the tightening loop extending through the retaining opening to an eyelet and being engaged through a tightening opening formed transversely in the prop; the filamentary line further comprising traction means which extend the tightening loop from the tightening opening, the traction means extending inside the prop at least to a control end actuatable from the proximal end of the prop; and        at least one releasable retaining member, the eyelet being engaged releasably on the retaining member.        
Such a device is used for releasing tubular endoprostheses, commonly referred to as “stents”, within a blood vessel.
A device of the above-specified type is described in EP-A-0 707 462. An endoprosthesis is mounted coaxially on two hollow props suitable for sliding relative to each other. The endoprosthesis is held in its retracted state using two filamentary lines binding its ends. The filamentary lines are engaged respectively in distal and proximal retaining openings formed respectively in each of the props.
To release the endoprosthesis, the props are moved to slide relative to each other so that the distance between the retaining openings decreases.
Reducing this distance causes the filamentary lines to relax and consequently causes simultaneously the two ends of the endoprosthesis to be deployed.
During deployment, the line holding the proximal end of the endoprosthesis moves towards the proximal end of the prop since the prop is moved towards the distal end of the endoprosthesis.
Nevertheless, such devices do not give full satisfaction. The device does not enable first one and then another one of the ends of the endoprosthesis to be deployed in succession, and in some cases that can lead to rather inaccurate positioning within the blood vessel.